Processes of dyeing cellulosic materials with inorganic metallic compounds



PROCESSES OF DYEING CELLULOSIC MATERIALS WITH INORGANIC METALLICCOMPOUNDS Percy Field Crosland, Bury, England No Drawing. ApplicationNovember 21, 1955 Serial No. 548,234 Claims priority, application GreatBritain December 1, 1954 2 Claims. (Cl. 8-52) This invention relates toan improved process for dyeing fabrics or yarns of cellulosic materialwith inorganic metallic compounds.

It is well known and is common practice to produce fast dyeings on piecegoods made of cotton, flax and such synthetic fibers as are essentiallycellulosic in nature such as viscose by impregnating the scouredmaterial with a solution containing a suitable metallic salt or amixture of such metallic salts, drying the fabric and then precipitatingthe hydroxides or basic salts of the metals in and on the fibres bytreatment with alkalis or other solutions of sufficient basicity, themetal salts most frequently employed being the salts of iron andchromium and an admixture of them. The method above described producesthe dye well known as mineral khaki.

It is also well known that if soluble iron salts are used alone in theprocess described above then yellow to brown shades, often described asiron buff, can be produced on cellulosic fibres.

It is known moreover, that the treatment of cellulosic fabrics byconcentrated solutions of sodium or potassium hydroxides before thedyeing process, or in the course of it at the precipitating stage, orsubsequent to it, substantially alters the shade and generally increasesits depth.

In the following specification and claims the term inorganic iron saltsis intended to cover not only an inorganic iron salt per se but also amixture thereof with a further inorganic metal salt or salts and theterm precipitated salt is intended to cover the hydroxide or basic saltor salts of the metal precipitated on or in the fibres.

It has now been found that if dry cloth dyed by any of the ways abovedescribed by impregnation with an inorganic iron salt and thenprecipitating the precipitated salt is heated to a high temperature fora short time the shade is deepened and made redder, the extent of thechange depending upon the time of heating and on the temperatureattained by the fabric and is the more striking as the proportion ofiron salts used in any mixture of salts for the impregnation isincreased.

An understanding of the invention will be obtained from the followingexamples, but it is to be understood that these are only illustrativeand that the invention is not limited thereto.

Example 1 A well scoured cotton fabric is impregnated with a 15 percentsolution of crystalline ferrous sulphate having the formula FeSO .7H O,is then well squeezed so that the pick-up of the liquor is about ninetypercent of the weight of the dry cloth and is dried in hot air. Atreatment of the material with a cold ten percent solution of sodiumhydroxide precipitates either ferrous hydroxide or a basic ferroussulphate or mixtures thereof on or in the fabric which, when washed andhung in air oxidizes to the ferric condition. This results in a brownishyellow shade but when the washed and dried cloth is heated to 145 C. forfive minutes the shade is much deeper and redder.

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Example 2 If Example 1 is modified by using an excess of a solution ofmercerising strength to precipitate the ferrous hydroxide or basicferrous sulphates, the shade obtained will be richer and deeper thanobtained in Example 1 and a subsequent heating of the washed and driedfabric to C. for five minutes will make the shade still deeper andredder.

Example 3 If instead of using. a ferrous sulphate solution as in Example1 a solution of ferric chloride is used which is equivalent to theconcentration of ferrous sulphate specified in Example 1 and issufiiciently basic not to weaken the cloth when carefully dried, then bythe alkaline treatment as given in Example 1, the ferric hydroxide orbasic ferric sulphate is precipitated directly which avoids the need foroxidation. This results in a brown shade and if the fabric is washed,dried and subsequently heated to 165 C. for five minutes the shade ismuch deepened and reddened thereby.

Example 4 Cotton cloth is dyed by evenly impregnating it with a solutioncontaining ten percent of hydrated ferrous sulphate and five percent ofchromium sulphate having the formula Cr (SO.,) which has been madeslightly basic. The fabric is then dried and subsequently the metalliccompounds are precipitated by a hot solution of sodium hydroxide of 8%concentration, the resulting shade when washed, dried and heated to 135C. for ten minutes is deepened and reddened.

In the specification of British Patent No. 730,601, there is described aprocess whereby the shade obtained is made deeper and redder in tone ifa cellulosic fabric or yarn is impregnated with a solution of a ferroussalt and ferrous hydroxide or a basic ferrous salt precipitated byimmersion in an alkaline solution and then the material is againimpregnated and immersed in an alkaline solution. It is now found thatif the material which has been coloured by the double treatment ofimpregnation, drying and precipitation, is heated for a few minutes at atemperature of between 130 C. and C. the colour is further deepened andreddened.

I claim:

1. In a process for obtaining deeper dye shades more nearly approachingred for cellulosic textile material which has been dyed by (1)impregnating said material with a solution containing an inorganic ironsalt; (2) treating saidmaterial with an alkaline solution to precipitateat least one material selected from the group consisting of the basicsalts and hydroxides of said inorganic iron salt; and (3) drying saidmaterial: the improvement which consists essentially in subjecting suchdyed, dried material to a temperature of at least approximately 120 C.,said temperature being insufiiciently high to damage the fibers of saidmaterial, for a sufficient period to permit the shade of the dyedmaterial to attain the desired deepness of shade.

2. In the process defined in claim 1, the temperature to which saidmaterial is heated not exceeding about C.

References Cited in the file of this patent UNITED STATES PATENTS OTHERREFERENCES Schofield: Paint Manufi, June 1941, vol. 11, No. 6, pp.181-184.

1. IN A PROCESS FOR OBTAINING DEEPER DYE SHADES MORE NEARLY APPROACHINGRED FOR CELLULOSIC TEXTILE MATERIAL WHICH HAS BEEN DYED BY (1)IMPREGNATING SAID MATERIAL WITH A SOLUTION CONTAINING AN INORGANIC IRONSALT, (2) TREATING SAID MATERIAL WITH AN ALKALINE SOLUTION TOPRECIPITATE AT LEAST ONE MATERIAL SELECTED FROM THE GROUP CON SISTING OFTHE BASIC SALTS AND HYDROXIDES OF SAID INORGANIC IRON SALT, AND (3)DRYING SAID MATERIAL: THE IMPROVEMENT WHICH CONSISTS ESSENTIALLY INSUBJECTING SUCH DYED, DRIED MATERIAL TO A TEMPERATURE OF AT LEASTAPPROXIMATELY 120*C., SAID TEMPERATURE BEING INSUFFICIENTLY HIGH TODAMAGE THE FIBERS OF SAID MATERIAL, FOR A SUFFICIENT PERIOD TO PERMITTHE SHADE OF THE DYED MATERIAL TO ATTAIN THE DESIRED DEEPNESS OF SHADE.